Historically, in the forest resource industry, there has been a problem in disposing of wood residue generated by a solid wood products processing mill in manufacturing its solid wood products such as beams, timbers, planks, boards and planed products. Traditionally, wood residue such as sawdust, wood chips, bark, log ends, shavings, knots, and the like, have been disposed of by burning the wood residue directly as is and in the volumes as it is produced by the wood manufacturing process in an incinerator known in the trade as a "TeePee burner". TeePee burners are old fashioned, highly inefficient, perform poorly and generate noxious gases and ash products. TeePee burners continue to be used but are now tolerated mainly in rural areas. Even so, there is some reluctance to force their replacement with other more efficient and expensive incinerators (such as OLIVINE .TM.) due to the fact that even an OLIVINE incinerator cannot meet most current government enacted environmental standards.
Due to the enactment of more stringent air pollution regulations by the Department of Environment, among others, and the required phasing out of existing inefficient waste wood product burners not meeting those regulations, such as TeePee burners, new apparatus and new methods of residue handling/incineration or recovery for useful products are required. Even so, a problem remains with what should be done to improve the efficiency of existing burners. One way is to control the rate of wood residue feed to incinerators to allow them to function more efficiently rather than to be constantly overfed or under-fed due to variances in mill waste production and stoppages for lunches, coffee breaks, breakdowns, periods between shifts, the graveyard period, and the like.
A number of patents disclose various designs of systems for feeding fuel to fire burners or controlling waste disposal.
U.S. Pat. No. 4,489,664, granted Dec. 25, 1984, Williams, discloses a closed loop fuel feeding system for multiple direct fired burners. A conduit system is associated with a fuel grinding mill to form a closed loop for conducting the flow of fuel and air back to the mill in excess of the fuel and air not released from the conduit system to the burners. The system is designed to be used with finely ground coal. The closed loop circulation system enables the finely ground coal to be fed to a plurality of direct fired burners in relation to burner capacity to consume the fuel.
U.S. Pat. No. 5,425,316, granted Jun. 20, 1995, Malone, discloses a waste disposal system that has a first combustion chamber for incinerating waste material to produce ash and exhaust containing gases and particulate matter, and a second combustion chamber for firing the exhaust containing gases and particulate matter. The system also includes a plurality of sub-systems working in cooperation with the first and second combustion chambers, and a control system to control the sub-systems to ensure a desired level of incineration of the waste in the first and second combustion chambers. The control system includes sensors disposed throughout the waste disposal system, and a central controller that continuously monitors the measured conditions and compares each of the measured conditions to a predetermined performance range.
Canadian Patent No. 1,210,995, granted Sep. 9, 1986, Caffyn et al., discloses an incineration system which includes a rotary primary oxidation chamber and a secondary oxidation chamber or after burner which receives gaseous products of combustion from the primary chamber. The primary oxidation chamber is a horizontally disposed rotary drum. The secondary oxidation chamber is vertically disposed. The secondary oxidation chamber includes baffles for blocking the flow of gases and other products of combustion from the lower portion of the primary oxidation chamber into the secondary oxidation chamber.
Canadian Patent No. 2,055,552, granted May 21, 1992, Morhard et al., discloses a hazardous waste incinerator which includes a rotary kiln which is comprised of six retort sections. The combusted waste is separated into ash and recoverable metals. Air flow is countercurrent to the flow of waste through the kiln. The exhaust gases are vented from the kiln entrance. The incinerator includes a secondary combustor to ensure destruction of any principal organic hazardous constituents. The incinerator also includes a control system. The control system is made up of a program-control processor unit which is connected by an optical/electrical interface to an optical data highway loop with parametric sensors for each sub-system.
Canadian Patent No. 2,112,740, granted Nov. 25, 1993, Lautenschlager et al., discloses a process for regulating the quantity of refuse to a refuse incinerator which disposes refuse and processes recyclable materials. The incinerator is designed to reduce and eliminate harmful or toxic substances such as exhaust gases and particulate such as flue dust and ashes in the exhaust gases. The system is designed to maintain approximately constant operating conditions during the incineration process. The system is intended to keep the amount of refuse delivered to or the depth of the refuse layer on a combustion grate approximately constant, regardless of net calorific value, and to prevent overloading or underloading of the grate.